[Xorp-users] BGP conditional route advertising

[Mihai Tanasescu]

Hello,


Already thought about that but I'm having problems with my provider's 
acceptance of those "splited" prefixes.
I'll try to look into the xorp code and see what I can change to achieve 
the conditional route advertising feature.


Robert Bays wrote:

> Mihai,
>
> If your CIDR block is large enough (/23 or greater) split your 
> supernet into two subnets.  Announce the supernet out your backup link 
> and the subnets out your primary link.  Most, if not all, traffic will 
> flow inbound through your primary link based on longest prefix match.
>
> Cheers,
> Robert.
>
> mihai at duras.ro wrote:
>
>> 1. I don't know if I'm that good with coding in regard to Xorp but I'll
>> give it a try.
>>
>> 2. I was taking about the following case:
>>
>> Provider --.> Upstream 1 ISP  --> Telia
>>
>> same Provider --> Upstream 2 ISP --> Level-3 let's say
>>
>> Telia will always return traffic to you via Upstream 1 ISP...but 
>> let's say
>> you'd like to use one link for all traffic (download and upload) and the
>> other one only as backup (financial reasons)
>>
>> That was what I was pointing at:)
>>
>> 3. Thought about the script option..but I was looking more at something
>> built-in...looks like I'll have to document myself and add it to the
>> existing code.
>>
>>
>>> On Fri, Sep 01, 2006 at 11:56:21AM +0300, mihai at duras.ro wrote:
>>>
>>>> I'll try adding a feature request then.
>>>>
>>>> Prepending is sometimes not enough.
>>>>
>>>> For example some upstream providers will always place a higher weight,
>>>> local pref,etc on a route received from a certain peer and thus render
>>>> the
>>>> as-path prepend unusable.
>>>
>>> Certainly. I'd say just about everyone places a
>>> higher local preference on their own customers,
>>> but that lpref won't be visible beyond your
>>> upstream so just about everyone else on the
>>> Internet will choose the best route based on the
>>> shortest AS-PATH.
>>>
>>>> What I want is:
>>>>
>>>> Announce my route over ISP1 while ISP1 is online (and don't receive 
>>>> any
>>>> traffic on the backup ISPs).
>>>> If ISP1 down then announce via ISP2.
>>>> If ISP2 down..and so on.
>>>
>>> You could probably do this via some form of shell
>>> script that polls to see if ISP1 is down or not
>>> and then add an advertisement via ISP2.
>>> or buy a Cisco.. or do some XORP coding :)
>>>
>>> Regards,
>>>    Kristian.
>>>
>>>
>>>>> On Fri, Sep 01, 2006 at 11:25:01AM +0300, mihai at duras.ro wrote:
>>>>>
>>>>>> Hello,
>>>>>>
>>>>>> Sorry if this has been asked before but I had no luck while
>>>>>
>>>> google-ing
>>>>
>>>>>> for
>>>>>> it.
>>>>>>
>>>>>> Does XORP support BGP conditional route advertising as Cisco does
>>>>>
>>>> with
>>>>
>>>>>> the
>>>>>> advertise map per-neighbor command ?
>>>>>
>>>>> As far as I know it does not, but it would indeed
>>>>> be a nice feature. You could add a feature request
>>>>> at http://www.xorp.org/bugzilla/index.cgi with a
>>>>> small description of what you want :)
>>>>>
>>>>>> I'm searching for a solution to advertise some prefixes on a backup
>>>>>
>>>> link
>>>>
>>>>>> only if the main link goes down (the default gateway is no longer
>>>>>> received
>>>>>> on it with an AS-PATH of the neighbors AS)
>>>>>
>>>>> Isn't prepending your as-path enough?
>>>>>
>>>>> Regards,
>>>>>     Kristian.
>>>>>
>>>>> -- 
>>>>> Kristian Larsson                                   KLL-RIPE
>>>>> Network Engineer                      Net at Once [AS35706]
>>>>> +46 704 910401                 kristian at spritelink.se
>>>>>
>>>>
>>
>>
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>> Xorp-users at xorp.org
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>


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